CN1331586C - Composite photocatalytic reaction system for eliminating environmental pollutants in air or water efficiently - Google Patents

Abstract

The present invention relates to a composite photocatalytic reaction system for efficiently eliminating environmental pollutants in air or water. The present invention can largely enhance the photocatalysis decomposition efficiency and activity stability of photocatalysts to environmental pollutants. The present invention comprises a water decomposing hydrogen making reactor and a pollutant photocatalysis decomposing reactor, and is formed by coupling a water decomposing hydrogen making reactor unit and a pollutant photocatalysis decomposing reactor unit, and an air or oxygen pipeline which is communicated with an air source containing pollutants is arranged at the front of the water decomposing hydrogen making reactor. The previous unit is a photocatalysis water decomposing hydrogen making system which provides needed hydrogen gas to the next photocatalysis reaction unit for decomposing pollutants; the two systems can be combined into a whole, and can be coupling in separated columns. The present invention can achieve high efficiency photocatalysis eliminating effects to pollutants. The present invention can not only used for eliminating pollutants in the air, but also be used for eliminating pollutants in water.

Description

Composite photocatalytic reaction system for efficiently eliminating air or water environmental pollutants

Technical field:

The invention relates to the technical field of photocatalysis and its environmental pollution control. Specifically, the invention relates to a composite photocatalytic reaction system for efficiently eliminating environmental pollutants in air or water.

Background technique:

Photocatalytic technology based on semiconductor oxides has a wide application background and great significance in clean energy, environmental protection and new materials. However, the quantum efficiency of _TiO2 photocatalyst is too low, the utilization rate of solar energy is not high, and other semiconductors, such as CdS and ZnO, are easy to be photocorroded and have poor stability. These problems seriously restrict the large-scale and wide application of photocatalytic technology. In order to improve the efficiency of photocatalysts and photocatalytic processes, a lot of exploration and research have been carried out at home and abroad. The semiconductor photocatalysts include doping various metal and non-metal elements, compounding the second semiconductor or even the third semiconductor, loading on the carrier, changing the acidity, manufacturing lattice defects, making the particles nanometer, etc. Extensive research on modification, modification and preparation; various external fields such as electric field, microwave field, ultrasonic field and plasma field have been added to the photocatalytic process to enhance the light absorption rate of the catalyst, the separation efficiency of photogenerated carriers and prolong the Its lifespan is an exploration for the purpose. These methods have improved the physical and chemical properties of the photocatalyst and the efficiency of the photocatalytic process to varying degrees, but the effect is still unsatisfactory. From the perspective of practical applications, taking _TiO2- based photocatalysts as an example, improving the photocatalytic conversion rate of pollutants and the activity stability of catalysts in the photocatalytic process are the most critical issues that must be solved for large-scale industrial applications of photocatalytic technology. question.

Invention content:

The object of the present invention is to overcome the above-mentioned defects, to provide a kind of high-efficiency elimination of air or water environmental pollutants that can be used for photocatalytic elimination of various inorganic and organic trace pollutants in air and water durably, efficiently and conveniently. composite photocatalytic reaction system.

The technical scheme of the present invention is as follows, and it is characterized in that it includes a water splitting hydrogen production reactor and a pollutant photocatalytic decomposition reactor, which is formed by coupling the water splitting hydrogen production reactor and the pollutant photocatalytic decomposition reactor through pipelines. Before the water splitting hydrogen production reactor, there is also a pipeline communicated with the air containing pollutants or the oxygen source containing pollutants; or the water splitting hydrogen production reactor and the pollutant photocatalytic decomposition reactor are combined into one with simultaneous water decomposition A dual-function single reactor with the functions of hydrogen production and pollutant photocatalytic decomposition; the pollutant photocatalytic decomposition reactor and the dual-functional single reactor are illuminated by a light source.

The system of the invention can greatly improve the photocatalytic decomposition efficiency and activity stability of the photocatalyst to environmental pollutants. The inventors discovered for the first time in the world that in the gas phase photocatalytic reaction, a hydrogen-oxygen mixture containing a small amount of hydrogen is used instead of oxygen or air as an oxidant, and in the suspension photocatalysis, oxygen or air aeration is changed to a hydrogen-oxygen mixture Gas aeration provides the oxidant required for the photocatalytic process, which can greatly improve the photocatalytic conversion rate and stability of pollutants.

The photocatalyst particles are used as a fixed bed for the gaseous pollutants, and the photocatalyst particles are suspended in the solution for the pollutants in the solution. The photocatalytic decomposition of gaseous pollutants uses hydrogen-oxygen mixed gas or hydrogen-air mixture containing pollutants as the carrier gas, and the photocatalytic decomposition of pollutants in the solution uses hydrogen-oxygen mixed gas bubbling aeration. According to the photoresponse ability of photocatalyst, ultraviolet light or visible light is used as light source to irradiate the catalyst bed or suspension, the pollutants in the mixed gas or aqueous solution will be efficiently decomposed, and the process will maintain long-term high activity and stability.

The mechanism by which the addition of a small amount of hydrogen to the carrier gas and aeration leads to the improvement of the efficiency and stability of the photocatalytic process has not been fully understood. According to preliminary studies, it is likely to be related to the structure and composition of the catalyst, and the dissociation and adsorption of oxygen and hydrogen on the surface of the catalyst. And so on. In the photocatalytic process, the catalyst effectively dissociates and adsorbs oxygen and hydrogen molecules at the operating temperature. The hydrogen atoms and oxygen atoms adsorbed on the surface of the catalyst are very active and easy to accept the photogenerated electrons and holes generated by semiconductor light, so that the formation of Hydroxyl radicals and superoxide radicals reduce the recombination rate of photogenerated electrons and holes, accelerate the decomposition of pollutants, and make the catalyst less likely to accumulate intermediates in the photocatalytic process and have self-regeneration capabilities.

Although it is common and convenient to add hydrogen to the reaction materials in conventional non-photocatalytic processes, for photocatalytic processes, adding hydrogen will greatly increase the cost and energy consumption of the process, which is incompatible with the pursuit of photocatalytic environmental pollution control technology. It runs counter to the concept of green environmental protection and low energy consumption. The present invention is a coupled photocatalytic reaction system for efficient photocatalytic elimination of air and water pollutants invented according to this discovery. This system does not need to provide an additional hydrogen source, and the hydrogen required for the reaction is generated by the system itself.

Description of drawings:

Fig. 1 is a schematic structural view of the composite photocatalytic reaction system for eliminating pollutants in the air according to the present invention.

Fig. 2 is a schematic structural view of the composite photocatalytic reaction system for eliminating pollutants in solution according to the present invention.

Fig. 3 is a schematic structural view of the composite photocatalytic reaction system for eliminating pollutants in solution according to the present invention.

Fig. 4 is another structural schematic diagram of the composite photocatalytic reaction system for eliminating pollutants in solution according to the present invention.

Fig. 5 is the structural representation of three kinds of photocatalytic hydrogen production units in the composite photocatalytic system used in the present invention

Fig. 6 is the schematic structural view of the hydrogen production unit by electrolysis of water in the composite photocatalytic system used in the present invention

Label description:

1- Air containing pollutants; 2- Purified air; 3- Light source; 4- Hydrogen production unit; 5- Conduit; 6- Quartz glass tube; 7- Power supply; 8- Oxygen or air aeration tube; 9- DC power supply; 10-connected to the photocatalytic reaction unit of pollutants; 11-photocatalyst; 12-photocatalyst + aqueous solution containing pollutants; 13-(photocatalytic water splitting catalyst + photocatalytic pollutant decomposition catalyst + aqueous pollutant solution) or (double Functional catalyst + pollutant aqueous solution); 14-photolysis water catalyst + aqueous solution; 15-electrode; 16-photocatalyst film; 17-aqueous solution containing pollutants; 18-aqueous solution; Metal electrode 1; 21-electrode 2; 22-electrolyte + aqueous solution.

Detailed ways:

As shown in Figures 1, 2 and 3, the present invention includes a hydrogen production reactor and a pollutant photocatalytic decomposition reactor. The hydrogen production reactor and the pollutant photocatalytic decomposition reactor constitute a composite photocatalytic reaction system. Before the hydrogen reactor, there is also a pipeline communicating with air or oxygen or a gas source containing pollutants.

The hydrogen production reactor is an electrolytic water hydrogen production system or a photocatalytic water splitting hydrogen production system or a two-electrode hydrogen production system. Photocatalytic hydrogen production system. The hydrogen production reactor provides the trace amount of hydrogen required by the pollutant photocatalytic decomposition reactor. The two reactors are connected by a pre-installed gas source, which can be air or oxygen or air containing pollutants. ) A photocatalytic water splitting hydrogen production system or a two-electrode hydrogen production system is irradiated by a light source.

As shown in Figures 1, 2 and 3, this composite photocatalytic reaction system can be an all-photocatalytic coupled reaction system consisting of a photocatalytic self-supplying hydrogen unit and a photocatalytic pollutant decomposition unit. The former unit is a photocatalytic water splitting hydrogen production system, which provides the required hydrogen for the latter photocatalytic reaction unit that decomposes pollutants. The catalyst used may be two compounds with different compositions and structures, one for photocatalytic water splitting to produce hydrogen and the other for photocatalytic decomposition of pollutants; at this time, two independent electrolytic water hydrogen production units and photocatalytic decomposition of pollution Units are connected by pipes. The pollutant photocatalytic decomposition reactor is irradiated by the light source, and the photocatalytic water splitting hydrogen production system or the two-electrode hydrogen production system as the water splitting hydrogen production reactor is also irradiated by the light source.

As shown in Figure 4, this composite photocatalytic reaction system can also be a single coupled system, a dual-function single reactor with dual functions of water splitting hydrogen production reaction and pollutant photocatalytic decomposition in one reactor. The functional single reactor is illuminated by a light source. The catalyst used is a bifunctional photocatalyst with two properties or a mixture of two catalysts, which can simultaneously photolyze water and degrade organic matter in aqueous solution (Figure 4A); this system can also be composed of a bifunctional photocatalyst attached Electrode composition, water splitting and photocatalytic decomposition of organic matter are coupled (Fig. 4B).

This composite photocatalytic reaction system can also be a coupled reaction system composed of an electrolyzed water hydrogen production unit and a photocatalytic decomposing pollutant unit, and the two units can also be combined into one or combined separately. For the integrated system, the hydrogen production and the photocatalytic decomposition of pollutants occur in the same reactor; while for the combined system, the electrolysis system independently provides hydrogen for the photocatalytic pollutant decomposition system. At this time, they are independent of each other. The electrolytic water hydrogen production unit and the photocatalytic pollutant decomposition unit are connected by pipelines.

Regardless of the above-mentioned working methods, it can achieve the effect of efficient photocatalytic elimination of pollutants, which can be used for the elimination of pollutants in the air and water.

Example 1

A photocatalyst is added to the aqueous solution or it is loaded on the electrode material as a film and placed in the aqueous solution, and the light source is placed in the solution or the container is equipped with a light source to form a photocatalytic water splitting system. Its characteristic function is: apply sunlight or artificial light source with a wavelength of 200-800nm to the catalyst in the water photocatalytic photodecomposition system to decompose water on the surface of the catalyst to generate hydrogen and oxygen. This photocatalytic hydrogen production unit can have various structures. The photocatalytic hydrogen production unit shown in Figure 5 is a suspension system, that is, the photocatalyst is added to water, and the water is decomposed into hydrogen and oxygen by irradiating with ultraviolet light or visible light from outside or inside the tube. An electrode system coated with a photocatalyst can also be used as a photocatalytic hydrogen production unit.

Put another photocatalyst into a quartz glass reactor or load it on other carriers and add a light source (artificial light sources include various forms of mercury lamps, fluorescent lamps, or visible light sources, sunlight) to form a gas-phase photocatalytic reaction unit (see Figure 1); or add catalyst particles (supported or unsupported) to the solution containing pollutants and add a light source to form a liquid-phase photocatalytic reaction unit, see Figure 2 and Figure 3. The features and functions of this unit are: applying sunlight or artificial light sources with a wavelength of 200-800nm to the catalyst to photocatalytically decompose pollutants in the gas phase or in water; the photocatalyst in the photocatalytic reactor can be titanium dioxide, Metal (such as Fe, Co, Ni, Pt, Pd, Ru, Rh, etc.) doped modified titanium dioxide, solids composited with other oxides, supported titanium dioxide and films; it can also be other photocatalysts, such as CdS , ZnO, Fe ₂ O ₃ , SnO ₂ , ZrO ₂ and their modified composites; it can also be InVO ₃ , SnCdS solid, or electrode materials including metal substrates formed after loading these catalysts on metal substrates. The pollutant photocatalytic decomposition system can also have various structures. For the pollutants in the gas, the catalyst can be packed in a packed fixed bed, or it can be loaded on porous ceramics, activated carbon, activated carbon fiber, glass fiber, metal substrate and other materials in a thin film. arrangement. The light source can be installed externally or internally to illuminate the catalyst.

For gaseous pollutants, the required carrier gas is supplied by an air compressor pump, air cylinder, oxygen cylinder and the previous unit, that is, the air or oxygen stream containing pollutants is passed through the first unit to bring out the gas generated by the unit. Hydrogen and oxygen get a hydrogen-oxygen-pollutant mixture containing a small amount of hydrogen, which will pass through the second unit as the carrier gas of the second unit, so that the pollutants and hydrogen in it will be eliminated by photocatalytic reaction. For pollutants in solution, such as pollutants in water, the second unit is a liquid-phase photocatalytic reaction unit, and the carrier gas is also supplied by an air compressor pump, air cylinder, oxygen cylinder and the previous unit, which passes through the first Oxygen or air containing a small amount of hydrogen is formed during the unit, and the carrier gas is used as the aeration gas for the second unit solution.

The composite photocatalytic system composed of gas source and the above two units can be used for efficient photocatalytic treatment of pollutants contained in gas phase and solution. Pollutants include: various organic and inorganic pollutants contained in air and water, such as aldehydes, phenols, alcohols, ethers, alkanes, aromatics, heterocyclic compounds, dyes, pesticides, military poisons, nitrogen oxides , sulfur oxide, etc.

Example 2

Insert two platinum electrodes into an aqueous solution containing a small amount of electrolyte to form a common water electrolysis device, apply a certain voltage to electrolyze water to generate hydrogen and oxygen, and form a hydrogen production unit that meets the needs of the second unit as required. The characteristics and functions of this device are: it can conveniently control the release amount of hydrogen and oxygen, and the generated gas can be conveniently brought into the photocatalytic pollutant decomposition unit by the pre-gas.

The photocatalytic pollutant decomposition unit is the same as that in Embodiment 1.

The electrolytic water hydrogen production unit used in this composite photocatalytic reaction system adopts the conventional electrolytic water device shown in Figure 6.

Example 3

As shown in Figure 4, for the photocatalytic decomposition of pollutants in solution, a single reactor can be used to simultaneously suspend a photocatalyst for photolysis of water and a photocatalyst for decomposition of pollutants in an aqueous solution containing pollutants, The suspension is irradiated with ultraviolet light or visible light from the outside or inside, and the hydrogen and oxygen generated by the photocatalyst for water splitting are utilized by the photocatalytic process of pollutants; dual-functional photocatalysts can also be used to quickly decompose pollutants in the same way; The electrode system can also be used to coat the photocatalyst on the surface of the electrode and apply a certain bias voltage and light to couple the photocatalytic hydrogen production process of the system with the photocatalytic decomposition process of pollutants to achieve the purpose of efficiently decomposing pollutants.

Claims (7)

1, the composite photocatalytic reaction system of environmental contaminants in a kind of efficient elimination air or the water, it is characterized in that: it comprises water decomposition hydrogen-manufacturing reactor and pollutant photocatalysis Decomposition reactor, be that water decomposition hydrogen-manufacturing reactor and pollutant photocatalysis Decomposition reactor are constituted by the pipeline coupling, before the water decomposition hydrogen-manufacturing reactor, also be provided with the air that contains pollutant or contain the pipeline that the oxygen source of pollutant communicates; Perhaps with water decomposition hydrogen-manufacturing reactor and the synthetic difunctional single-reactor that water decomposition hydrogen manufacturing and pollutant photocatalysis Decomposition function are arranged simultaneously of pollutant photocatalysis Decomposition reactor; Pollutant photocatalysis Decomposition reactor and difunctional single-reactor are shone by light source.

2, the composite photocatalytic reaction system of environmental contaminants in efficient elimination air according to claim 1 or the water, it is characterized in that: to the photocatalysis Decomposition of water pollutant, adopt difunctional single-reactor, be simultaneously a kind of photochemical catalyst of photodissociation water and the photochemical catalyst of pollutant decomposition to be suspended in the reactor that contains the pollutant aqueous solution jointly, in the aqueous solution that contains pollutant or the reactor outside with ultraviolet light or visible light source irradiation suspension, the hydrogen and the contaminated thing photocatalytic process of oxygen that are produced by photodissociation water catalyst are utilized; Perhaps adopt difunctional single-reactor and adopt the difunctional photochemical catalyst in the aqueous solution, play photodissociation water and degradation of organic substances simultaneously, from the aqueous solution that contains pollutant inner or from the reactor outside with ultraviolet light or radiation of visible light suspension; Perhaps adopt electrode system, bifunctional catalyst is coated in electrode surface, electrode inserts and to contain in the reactor of pollutant, applies bias voltage and illumination, makes photocatalysis produce hydrogen process and pollutant photocatalysis Decomposition process and carries out simultaneously and coupled reaction takes place.

3, the composite photocatalytic reaction system of environmental contaminants in efficient elimination air according to claim 1 or the water, it is characterized in that: the water decomposition hydrogen-manufacturing reactor is a water electrolysis hydrogen production system or photocatalysis water decomposition hydrogen generating system or two electrode system for producing hydrogen, described two electrode system for producing hydrogen are that electrode surface is coated with the water decomposition catalyst for preparing hydrogen, constitute one two electrode photocatalysis system for producing hydrogen; Described photocatalysis water decomposition hydrogen generating system or two electrode system for producing hydrogen are shone by light source.

4, the composite photocatalytic reaction system of environmental contaminants in efficient elimination air according to claim 3 or the water is characterized in that: described pollutant photocatalysis Decomposition reactor comprises quartz glass tube or container, light source, solid photochemical catalyst and contains the aqueous solution of pollutant; The solid photochemical catalyst is suspended in the aqueous solution that contains pollutant, and places quartz glass tube or container, light source to be placed in the center or the top of the aqueous solution that contains pollutant, from top or internal irradiation contain the aqueous solution of pollutant; Quartz glass tube or container have a gas vent and inlet.

5, the composite photocatalytic reaction system of environmental contaminants in efficient elimination air according to claim 3 or the water, it is characterized in that: described pollutant photocatalysis Decomposition reactor comprises outer tube, quartz glass tube, light source, pollutant photocatalysis Decomposition catalyst, gas pollutant; Photochemical catalyst is loaded in the described quartz glass tube, or photochemical catalyst loaded on places on the carrier in the described quartz glass tube; Quartz glass tube places in the outer tube, and light source places the gap that quartz glass tube is outer and outer tube is interior, and light shines gas pollutant by quartz glass tube, and quartz glass tube has gas pollutant outlet and inlet.

6, according to the composite photocatalytic reaction system of environmental contaminants in claim 2 or 3 or 4 or 5 described efficient elimination air or the water, it is characterized in that: described catalyst comprises photodissociation water catalyst, pollutant decomposition catalyst or bifunctional catalyst, they are titanium dioxide or by one or more the titanium dioxide solid of transient metal doped modification among Fe or Co or Ni or Pt or Pd or Ru or the Rh, perhaps InVO ₃, the SnCdS solid, or on metallic substrates the film of these catalyst of institute's load, or the electrode material that comprises metallic substrates that behind these catalyst of load on the metallic substrates, forms.

7, the composite photocatalytic reaction system of environmental contaminants in efficient elimination air according to claim 6 or the water, it is characterized in that: described light source is that sunshine or wavelength are the artificial light source of 200～800nm, and artificial light source comprises mercury lamp, the fluorescent lamp of different shape.

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